This invention relates to multi-ply absorbent, soft paper products useful as towels, napkins, wipes and the like. The invention is also concerned with methods and apparatus for attaining such absorbent paper products utilizing an efficient, suitable and generally minimal amount of adhesive to secure attachment of creped tissue webs to form a multi-ply sheet product.
It is known to provide embossed webs and to laminate them into the form of a sheet by adhesive attachment on a commercial basis. This may be done by any of several methods. One common method is to apply adhesive to the embossment surfaces of one of the webs of a sheet product and uniting at the embossment surfaces of the other web. In this instance for a two-ply web, each web is separately embossed and remains in contact with their respective separate embossing rolls. Adhesive is applied in a thin layer to the embossment surfaces of one of the webs with commercially available adhesive applicating equipment and both webs are joined at their embossment surfaces in the nip formed by the mated steel embossing rolls. This method provides a high bulk product having good quality ply attachment and works satisfactorily with discrete peg types of embossing patterns. With other types of embossing patterns, particularly gross patterns consisting of continuous line or embossed line patterns, this method results in application of adhesive to the entire land area of the sheet embossments, even though adhesive attachment may be obtained at a small portion of the total embossed land area, by utilizing for embossing, roll patterns which are in crossing relationship. The result is the use of more total adhesive than necessary for ply attachment purposes, which increases the product cost and also stiffens the product structure.
The present invention is an improvement on prior art practices in that adhesive is applied in well spaced adhesive zones, and the adhesive zones define embossments which are superposed on more gross embossments of the web product. This is accomplished by securing the webs together in a combining nip formed by a pair of cooperable embossing rolls having particular characteristics. The embossing rolls for the purpose each have a series of alternating ribs and grooves disposed about its periphery; the ribs of one roll have land areas and projections extending above the land areas separated by the land areas, and the ribs of the other roll have land areas and recesses lying below and separated by these last mentioned land areas of the second roll. The projections of one roll in the rotation of the rolls is receivable in mating recesses of the other said roll. In a further embodiment each of the rolls may have projections which cooperate with the receses of the other roll.
The projections of the embossing roll support a web for the receipt of adhesive only in the zone of the projection. Since such projections may be conveniently formed by etching, grinding or the like to a very small size, the adhesive application in an adhesive zone may be quite readily limited. Such leads to good flexibility in the webs and final sheet and is conserving of adhesive.
Another advantage for the above embossing and combining method is that it results in a product having an esthetically pleasing appearance. The use of continuous line types of embossing patterns produces a product having the same appearance on both sides. With some types of line patterns, the product may lack attractiveness because of the gross nature of the embossments. By providing the continuous lines embossments of one web with spaced projections and the other with spaced recesses, a more textured or woven type appearance is obtained in the product. The laminated product still has the same general appearance on both sides. However, the embossment line recesses on one of the webs prior to lamination become slightly raised projections as received in the finished product. Similarly, the embossment line raised projections of the other web become slight recesses after lamination in the finished product. These projections and recesses being confined to the continuous line embossments area tend to break up the continuity of the embossments and result in a more pleasing pattern appearance. In fact, the product attains somewhat of a woven fabric appearance.